The present invention relates to a steering lock device for vehicles.
In a conventional steering lock device, the drive force of a motor to electrically rotate a key cylinder or the force applied by a user to manually rotate the key cylinder moves a lock bar so that the lock bar is engaged with and disengaged from a steering shaft. The steering shaft is locked when engaged with the lock bar.
FIGS. 8A and 8B show a steering lock system 101 described in Japanese Patent Laid-Open Publication No. 2003-276564. The steering lock system 101 includes a sleeve assembly 102, a steering shaft assembly 103, a steering wheel 104, and a steering lock device 105. When a force (impact force) pushing the steering wheel 104 toward the front of the vehicle exceeds a predetermined value, the sleeve assembly 102 and steering shaft assembly 103 collapse to absorb the force.
The sleeve assembly 102 is formed by an inner sleeve 102a and an outer sleeve 102b. The inner sleeve 102a is arranged forward to the outer sleeve 102b in the vehicle. The basal portion (front end) of the inner sleeve 102a is connected to a base 106 fixed to the vehicle. The distal portion (rear end) of the inner sleeve 102a is received by the basal portion (front end) of the outer sleeve 102b.
A breakaway bracket 107 is arranged on the distal portion (rear end) of the outer sleeve 102b. The breakaway bracket 107 is formed by an engagement ring 108, which is fixed to the outer surface of the outer sleeve 102b, and a fixed hook 109, which is engaged with the engagement ring 108 and fixed to the vehicle body. When force pushing the outer sleeve 102b toward the front of the vehicle exceeds a predetermined value, the force is transmitted to the fixed hook 109 via the engagement ring 108 thereby breaking the fixed hook 109. This disengages the fixed hook 109 from the engagement ring 108 and enables the outer sleeve 102b to move toward the front of the vehicle.
Bearings 110 and 111 support the steering shaft assembly 103 in a manner rotatable relative to the sleeve assembly 102. The steering shaft assembly 103 includes a front shaft 103a, a rear shaft 103b, and a seat member 118 fixed to the rear shaft 103b. Part of the front shaft 103a is a spline shaft 112. The rear end of the spline shaft 112 is received in a spline boss 113 formed at the front end of the rear shaft 103b (see FIG. 9). The engagement between the spline shaft 112 and the spline boss 113 integrally rotates the shafts 103a and 103b. The shaft 103b is axially movable relative to the shaft 103a. A steering wheel 104 is fixed to the rear end of the rear shaft 103b. 
The steering lock device 105 will now be described with reference to FIG. 10. The steering lock device 105 includes a main body portion 114 having a housing, a lock bar 115 arranged in the housing and moved by an actuator, and a mounting portion 116 for mounting the main body portion 114 to the outer sleeve 102b. 
The mounting portion 116 has a curved surface 116a extending along the outer surface of the outer sleeve 102b. The steering lock device 105 is fixed to the outer sleeve 102b by fastening a fastening member 117 to the mounting portion 116.
The seat member 118, which is fixed to the rear shaft 103b, resembles a spur gear or the steering wheel of a vessel and has a plurality of radially extending projections 118a. The seat member 118 rotates integrally with the steering shaft assembly 103. A plurality of engaging recesses are defined between the projections 118a of the seat member 118. Rotation of the steering shaft assembly 103 is restricted when the distal portion of the lock bar 115 is received in one of the engaging recesses.
The distal portion of the lock bar 115 is box-shaped. FIG. 10 shows the lock bar 115 in a state located at a lock position. When moved to the lock position, the lock bar 115 extends through the outer sleeve 102b, and the distal portion of the lock bar 115 is arranged in an engaging recess defined between two adjacent projections 118a of the seat member 118. Abutment between the distal portion of the lock bar 115 and the two projections 118a defining the engaging recess restricts the rotatable angle range of the steering wheel 104. This locks the steering wheel 104.
When the lock bar 115 is located at an unlock position, the distal portion of the lock bar 115 is separated from the engaging recesses of the seat member 118. Thus, the steering wheel 104 is unlocked and rotatable.
As shown in FIG. 11A, the main body portion 114 includes a support member 120, for supporting the lock bar 115, and a coil spring 121, for resiliently connecting the lock bar 115 and the support member 120.
The support member 120 is moved by a drive device (not shown). The movement amount (amount of protrusion from the main body portion 114) of the lock bar 115 varies in accordance with the movement amount of the support member 120. The coil spring 121 is compressed when the lock bar 115 is forced towards the main body portion 114. The compression of the coil spring 121 enables the lock bar 115 to be moved towards the main body portion 114 without changing the movement amount of the support member 120.
FIG. 11A shows the lock bar 115 in a state located at the unlock position and the distal portion of the lock bar 115 facing towards an engaging recess between the projections 118a of the seat member 118. When the support member 120 moves from the state of FIG. 11A until the lock bar 115 reaches the lock position, the steering wheel 104 is locked, as shown in the state of FIG. 11B.
FIG. 11C shows a state in which the lock bar 115 is located at the unlock position and the distal portion of the lock bar 115 faces towards one of the projections 118a of the seat member 118. When the support member 120 moves from the state of FIG. 11C until the lock bar 115 stops at a position where it abuts against the projection 118a, the coil spring 121 is compressed, as shown in the state of FIG. 11D. In the state of FIG. 11D, the lock bar 115 is not located at the lock position. Thus, the steering wheel 104 is not locked. When the steering wheel 104 is rotated from the state of FIG. 11D, the biasing force of the coil spring 121 moves the lock bar 115 to the lock position. Thus, the distal portion of the lock bar 115 is received in an engaging recess between the projections 118a to lock the steering wheel 104. In this state, as shown in FIG. 11B, the coil spring 121 is extended and the protrusion amount of the lock bar 115 becomes maximal. In this manner, even if the lock bar 115 faces one of the projections 118a, the coil spring 121 moves the support member 120 in a preferable manner.
The steering wheel 104, the rear shaft 103b, the seat member 118, the bearing 111, the outer sleeve 102b, the steering lock device 105, the fastening member 117, and the engagement ring 108 form a movable component group Mz, which moves integrally along the axis of the steering shaft assembly 103. When a force pushing the steering wheel 104 towards the front of the vehicle exceeds a predetermined value, the force is transmitted to the fixed hook 109 via the engagement ring 108 and breaks the fixed hook 109. This moves the movable component group Mz toward the front of the vehicle.
In the conventional steering lock system 101, a problem may occur unless a distal end face 115a of the lock bar 115 is accurately positioned at the unlock position. That is, the minimum amount of protrusion of the lock bar 115 from the main body portion 114 must be accurately determined as described below. FIG. 12 shows an example in which, when the lock bar 115 is in the unlock position, the distal end face 115a of the lock bar 115 protrudes inwards from the inner surface S of the outer sleeve 102b. If such a case, the collapse of the sleeve assembly 102 would be interfered when the lock bar 115 abuts against the open end 43 of the inner sleeve 102a. 
Therefore, as shown in the state of FIG. 13, when the lock bar 115 is located at the unlock position, the distal end face 115a of the lock bar 115 is arranged at an unlock level P1, which is outwards from the inner surface S of the outer sleeve 102b. When locking the steering wheel 104, the distal end face 115a of the lock bar 115 is located at a lock level P2. Accordingly, the lock bar 115 is moved by a distance corresponding to that between the unlock level P1 and the lock level P2 (drive distance L).
The steering lock device 105 becomes larger as the drive distance L of the lock bar 115 becomes longer. Accordingly, there is a demand for a compact steering lock device that shortens the drive distance L.